The answer depends upon which inhibitor you are interested in. Some inhibitors may be competitive or noncompetitive inhibitors that are not substrates. Some inhibitors may be competitive inhibitors that are alternate substrates with respect to the substrate you are using to monitor the reaction). Some inhibitors may be irreversible covalent inhibitors (not mechanism-based). Finally, some inhibitors may be mechanism-based inhibitors (also called suicide substrates) that form a covalent bond with the enzyme as a result of passing part way through the catalytic mechanism, but not getting released efficiently as products. In this last group, there may be inhibitors that are released with different degrees of efficiency (referred to as the partition ratio kcat/kinact).

In reply, the residence time, occupancy and concentration of inhibitor and turn over and mode of action of enzyme are major determinants.